Mobile devices such as cellular telephones, smart phones, and other handheld or portable electronic devices such as personal digital assistants (PDA), headsets, MP3 players, and the like have become popular and ubiquitous. As more and more features have been added to mobile devices, there has been an increasing need to equip these mobile devices with input mechanisms that accommodate numerous user commands and react to numerous user behaviors. For example, many mobile devices are now equipped not only with buttons, but also with capacitive touch screens by which a user, simply by touching the surface of the device, is able to communicate a variety of messages or instructions.
It is of increasing interest that mobile devices are capable of detecting the presence of, and determining with some accuracy the position of, physical objects located outside of the mobile devices and, more particularly, the presence and location of people who are using the mobile devices or otherwise are located nearby the mobile devices. By virtue of such capabilities, the mobile devices are able to adjust their behavior in a variety of manners that are appropriate given the presence and location of people or other physical objects.
Recently remote sensing devices such as infrared or near-infrared transceivers have are employed in some mobile devices to allow for the detection of people or objects even when not in physical contact with the mobile devices.
Generally, these devices require a package that provides not only protection from environmental influences such as heat, pressure or moisture, but also optical functionality. The wavelength of the radiation that reaches the sensor often needs to be restricted to the near-infrared. This requires an optical filter which is integrated in the assembly. This puts high demands on optical packaging technology, more particularly to a low cost optical cavity package with filter functionality.
Prior art has come up with compositions of epoxy resins for semiconductor integrated circuit encapsulation. Some solutions suggest a combination of an optical receiving element with an optical filter consisting of a plurality of laminated light transmission layers deposited on the surface of a color glass filter or consisting of a crystal. Few approaches describe optical module packages consisting of an opaque cavity and a clear mold encapsulation. For these cases the mold compound is in contact with the sensor and thus cannot be used applications in which the sensor surface needs to be isolated from its surroundings.